The aim of our studies continues to focus on the surface properties of cells of the pancreas using a variety of experimental approaches in order to determine at the biochemical level the nature of specific proteins that relate to specialized cell function. Studies on the mature guinea pig acinar cell will probe (employing biochemical and electron microscopic procedures) receptor sites for the secretagogue CCK-PZ using photoaffinity labeling analogs of CCK and quantitative electron microscopy of election-dense CCK analogs. A major part of our research effort is to be directed at a detailed biochemical analysis of specific cell surface glycoproteins whose appearance on developing pancreatic rudiments is temporally regulated and which may be involved in cell-cell interactions accompanying morphogenesis of the exocrine and endocrine portions of the gland. Functional correlates of cell surface properties with onset of secretagogue responsiveness will be studied using the above-mentioned probes for CCK receptors. Efforts will also continue to examine biochemically identifiable defects in cell surface glycoproteins which appear to be present in a differentiated rat pancreatic acinar cell tum r with the aim of determining if inductive influences by mesenchymal tissue from normal tissue can reverse the defect in cell-cell interactions in the tumor and lead to normal tissue organization in the same way that mesenchymal tissue regulates morphogenesis in the developing gland. These studies may provide insight into factors that regulate expression and maintenance of cell surface properties of pancreatic cells that ultimately lead to the coordinated yet specific functions of the exocrine and endocrine pancreas.